It's not just your friends following you on Facebook or Twitter. The cops are, too.
Law enforcement agencies around the world have used social media monitoring software to keep tabs on populations en masse, sweeping up their posts and tweets, giving police a bird's-eye view of what, say, Twitter users are broadcasting in a specific area, or about a particular topic. Tweeting from an Olympic stadium? Sharing a post with a hashtag supporting Black Lives Matter? Police may be watching that, in real time.
On the face of it, you might not have a problem with cops reading public social media posts or tweets: individuals presumably took the decision to put the information out there themselves. But law enforcement's monitoring of social media is not that simple.
"Social media monitoring is so much more than it first appears. Programs to monitor social media are rarely about manual review of public information," Amie Stepanovich, US policy manager at activist group Access Now, told Motherboard in a Twitter message.
Instead, these programs are often about learning new, and qualitatively different information from an individual's or communities' postings. That might be the 'mood' of a population, which can then be used to predict any upcoming instability, or if a group may start to protest, for example.
"Police have a huge challenge in monitoring social networks for the prevention and detection of crime due to the sheer volume of material across networks such as Twitter and YouTube," a spokesperson from the Metropolitan Police Service in London told Motherboard in an email. The MPS has made heavy use of social media monitoring tools.
Or, software can map a person's movements over time, based on the geolocation data attached to their posts, and other pieces of metadata that users may not realise they are beaming out, as it is not always easily accessible to someone just looking at Twitter normally.
"What law enforcement increasingly can do with social media looks very different from what the public can do," Rachel Levinson-Waldman, senior counsel from the Brennan Center for Justice at New York University School of Law told Motherboard in a phone call. According to The Daily Dot, Geofeedia, a particularly popular social media monitoring tool, also makes use of fake profiles in an attempt to gain access to even more information on behalf of law enforcement clients. This activity appears to be geared toward targeted individuals.
Indeed, these services may rely on special access to social media site data, which gives them more information than an ordinary user.
Last week, Facebook, Instagram and Twitter cut off access for Geofeedia, after it was used to monitor protests against the fatal police shooting of black teenager Mike Brown. In some cases, photos from social media posts had been run through facial recognition systems.
"Disproportionately tracking minority groups or minority communities; using hashtags that are related to legitimate political protest I think is very problematic," Levinson-Waldman said.
And just like any other surveillance capabilities, social media monitoring can go wrong.
In 2012, two young Brits were arrested in Los Angeles after tweeting that they were going to "destroy America." The pair, however, were using slang to describe partying.
Levinson-Waldman described the problem of context, as an "almost insurmountable hurdle."
"Not that these tools won't sometimes get some of this right, but it seems unlikely that they will be able to fully grasp that context in [all] situations," she said.
"Trying to determine what certain activity on social media means; what liking something means; what retweeting something means; and I think it's going to be important to tread very carefully in that context."
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